A produce grader or sorter that is useful for sorting tomatoes according to their colors is disclosed in U.S. Pat. No. 3,944,819 issued Mar. 16, 1976 to J. R. Sherwood. Tomato sorters constructed according to the teachings of that patent have been used successfully to separate undesired green tomatoes from desired red tomatoes. When such a tomato sorter is mounted on a tomato harvester that harvests tomatoes from the growing vines in the fields, a considerable quantity of dirt clods and rocks will pass to the sorter along with the harvested tomatoes. It is desirable that the sorter be able to distinguish dirt and rocks from the produce and reject them along with the undesired articles of produce. Although the above-mentioned system satisfactorily separated desirable and undesirable tomatoes, it was not as effective as desired in rejecting dirt clods and rocks.